Effects of administration of oxytocin on embryonic survival in cows supplemented with exogenous progestogen

Author

John Willard Lemaster

Date of Award

8-1996

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

F. Neal Schrick

Committee Members

Fred Hopkins, Alan Mathew

Abstract

Embryonic survival after administration of oxytocin (OT) was examined in 42 beef cows. All cows were bred by natural service and artificial insemination (Day 0) following synchronization of estrus. Cows were randomly assigned to receive 25 ml saline (CON; n = 10), ICQ lU OT + 20 ml saline (OT; n = 12), 100 lU OT + 1 g flunixin meglumine (OT+FM; inhibitor of prostaglandin endoperoxide synthase; n = 10), or 100 lU OT + lutectomy (OT+LUT; n = 10) administered i.m. at 0600, 1400, and 2200 h on Days 5-8 after mating. Lutectomies were performed by transrectal digital pressure at 0600 h on Day 5. All cows were fed 4 mg/hd/d of melengesterol acetate through Days 3-30 and were bled by jugular venipuncture at 0600 and 0700 h on Day 5 for determination of 13,14-dihydro-15-keto-PGF_2α (PGFM). Additionally, CON, OT and OT+FM cows were bled daily during their respective treatments and every other day from Days 9- 17 for determination of progesterone (P₄). Pregnancy rates were determined by transrectal ultrasonography at Day 30. Pregnancy rates were reduced in OT (33.3%) and OT+LUT (30.0%) groups compared to CON and OT+FM (80.0%; P = .03). Progesterone did not differ between groups during the treatment period; however, the OT group tended to have lower P₄ (1.7 ± .2 ng/ml) compared to CON (2.5 ± .3 ng/ml) from Days 9-17 (P = .05). Number of short cycles were increased in OT (n = 6/12) group compared to CON (n = 0/10; P = .009) and OT+FM (n = 1/10; P = .045). Mean changes in PGFM from the 0600 to 0700h bleed were different (P = .01) between the OT+LUT (31.6 ± .0 pg/ml) group and CON (-11.2 ± 10.6 pg/ml) and OT+FM (-13.8 ± 10.6 pg/ml) groups. Administration of oxytocin appears to decrease embryonic survival by stimulating uterine PGF_2α. These data confirm previous reports indicating that removal of the corpus luteum during progestogen supplementation and prior to PGF_2α administration increases embryonic survival through interruption of the luteal oxytocin-uterine PGF_2α feedback loop.

Recommended Citation

Lemaster, John Willard, "Effects of administration of oxytocin on embryonic survival in cows supplemented with exogenous progestogen. " Master's Thesis, University of Tennessee, 1996.
https://trace.tennessee.edu/utk_gradthes/6825